Among the many joints of the human body, the knee joint is the joint that connects the tibia with the femur. There are increasing number of patients whose knee joint has become irrecoverable due to abrasion of the knee joint, aging of the bone tissues, and accidents. The knee joint, which refers to the joint at the knee, is a joint located between the lower end of the femur and upper end of the tibia and the rear side of the patella (knee bone) and enables the leg to bend backwards at the knee.
The symptoms of most diseases in the patella may occur without a particular external wound and may result from a structural or functional anomaly of the patella-femur joint. If the leg is abnormally bent outwards or if the foot is severely outwardly crooked, an excessive force may be applied repeatedly on the patella-femur joint to cause osteomalacia of the articular cartilage. Disuse of the knee joint for extended periods may also cause problems, due to the atrophy and contracture of the quadriceps femoris muscle. If there is a structural anomaly in the patella-femur joint, an assister device may be worn to stabilize the patella, and if there is extensive damage, a surgical procedure of replacing the knee joint with an artificial knee joint may be considered.
Thus, in recent times, operations for surgically replacing irrevocably damaged joints with artificial knee joints have become widespread. In such an operation, an artificial knee joint is generally divided into the femoral member, which is coupled to the end of the femur, the tibial member, which is coupled to the end of the tibia, and the insert, which is positioned between the femoral member and the tibial member. The insert is coupled to an upper side of the tibial member, enabling the femoral member located above to perform a curving or rotating motion at the upper part of the insert.
FIG. 1 is a diagram illustrating the coupling and operational relationships between the tibial member, insert, and femoral member.
Referring to FIG. 1, an artificial knee joint is generally composed of a femoral member 10 coupled to the end of the femur F, a tibial member 30 coupled to the end of the tibia T, and an insert 50 positioned between the femoral member 10 and tibial member 30. The femoral member 10 couples to the end of the femur F to form an articular surface at the end of the femur F, the tibial member 30 couples to the end of the tibia T to form an articular surface at the end of the tibia T, and the insert 50 couples to the upper side of the tibial member 30 to be located between the tibial member 30 and the femoral member 10 and thereby allow the femoral member 10 to slide on the upper surface of the insert 50 to perform a curving or rotating motion and thus enable an articular movement by the artificial joint similar to that of an actual knee joint.
FIG. 2 is a perspective view of an insert unit for an artificial knee joint according to the related art, and FIG. 3 is a cross-sectional view across line A-A′ of FIG. 2.
Referring to FIGS. 2 and 3, the tibial member and the insert 50 are joined by an insert coupling portion 31 and coupler portion 55. However, with an existing insert and tibial member, the actions of bending and unbending the knee and the moment applied by rotations are concentrated on the insert coupling portion 31 and the coupler portion 55, so that there the problem occurs of the tibial member 30 and insert 50 becoming separated, etc.
Thus, there is the need for an insert of a novel structure that can improve the problems of the existing insert.